Strut construction for drafting machines



Sept. 13, 1949. J. A. HISLOP 2,431,556

STRUT CONSTRUCTION FOR DRAFTING MACHINES Filed March 5, 1946 2 Sheets-=Shee t 1 IN V EN TOR.

Sept. 13, 1949. J. A. HISLOP 2,481,665

STRUT CONSTRUCTION FOR DRAFTING MACHINES Filed March 5, 1946 2 Shecs-Sheet 2 r f m. M 23 LjW' 52 49 '1 30 2e Z7 Z2 INVENTOR. 'g/Ex/v 4 Milan ,VIIM

- with which such a machine is used.

. the baseline.

sible to the fingers of thedraftsman'.

Patented Sept. 13, 1949 STRUT CONSTRUCTION FOR DRAFTING ",MACHINES John A. Hislop, Pasadena, Calif., assignor to Vard; Inc., Pasadena, Calif a corporation of Californiar Application ltiarch 5, 1946,'Serial No.'652,104

This invention relates to a drafting machine "and has particular reference to a strut construction, whereby a drafting machine scale may be readily adjusted todifferent positions of orientation relative to a base line on a drawing In the art of drafting, it is the-common practice to employ drafting machines of thearticulated "arm type for the purpose of supporting one or morestraight edges upon a drafting board surface 'in such manner that irrespective of themanipulation of the straight edgesto various positions on -=thesurface of the drafting board. the str'ai'ght 1 edges will be maintainedin a definite angular relation with respect to a base line on'theboard.

will cause rotational movement 'of a scale supporting protector mechanism in equal angular 'but opposite directional movement'correspondi'ng to the 'movementof the articulated arms "relative "to a' fixed anchor and thus maintain the scales in a fixed oriented angular positionrelative to In prior constructionsof this type,it has usually been the practice to provide the scale supportingmechanism with devices which may be manipulated -to release the engagement between the scale support and the pulley on-that arm of the machine-to which it is attached whenever it is desired to change the oriented angular relation between the scale and the base line, such mechanism being generally awkwardjof access to 'thedraftsman or requiring laborious manipulation of mechanisms to effect a change in the angular relation of the scales.

It is, therefore, an object ofthis invention-' to provideia drafting machine of "the character 'set'i'orth, wherein adjustment [of the scale to different angular positions relative to the base --1ine may-beaccomplished by employing a quick release mechanism 'in'oneor both of the articu lated arms, the manipulationof which will iso a drafting machine of thecharacter set forth,

' wherein the effective length of one or both of the articulated arms may be lengthenedand short- -ened by a simple lever movement'readily accesboard 3 Claims. (CI. 33-79) Another object'of this invention is to provide 'a'release mechanism'of the character described,

which is especially adapted to drafting machines in which the arms are of the single rod or strut type and wherein'the-release mechanism is interposed in the single rod in such fashion that manipulation of the release mechanism through the relatively small-amount of movement will accomplish the necessary shortening of the arm to release the engagement of the band with the pulley. v v

-Other objects and advantages of this invention will" beapparent from-a study of the following specifications read in connection with panying drawings wherein; l p v 7 Fig. 1 is a plan view of a drafting machineof theendless band and pulley type equipped with a release mechanism constructed in accordance with this. invention; v v r r I a Fig. 2 is a fragmentary perspective view of a portion-of the strut structure comprising one of the arms shown in-the machine of Fig. 1, parts being broken away to show internal mechanisms; .Fign 3 is a longitudinal sectionalrview taken through that portion of the strut structure shown in- Fig. 2 and illustrating the 'position of. the. parts the accom- -.when the strut. is in its normally elongated position.

. Fig.4. is a sectional view similar to Fig. 3 but illustratingthe position of the parts when .the strut is in its contracted position; and

Fig. 5 is an exploded view illustrating the man ner of. assembly of the parts illustrated in Figs. 2, 3

and 4. y

Referring to the drawings,.I have illustrated arm I comprising a pair of headbracketsi and 4 spaced from each otherby means of astrut-rod 5 and having a pulley B at onevof its ends fixed to an anchor] which is, in turn, attached to one "edge of a drafting board 8 withwhich the machine to be used. 7

The opposite end of thejarm ,l is provided with a pulley 9, an endless band of steel tapelfl being "tionwith respect to the fixed pulley 6.

trained over the pulleys'fi and 9 in such fashion that any movement .of the arm Labout its pivot at the anchor I, willcause a corresponding rotational movement of the pulley 9 to maintain the pulley 9 in a fixed oriented angular relathis result. i i By referring particularly to Fig. 2, it wi11 b the pulley 9 at one of its ends and a pulley (not shown) at the other of its ends, over which is trained an endless band. I by which any rotational movement imparted to the arm 2 relative to the arm I or any rotational movement imparted to either or both of the arms I and 2 relative to the fixed pulley-5 will result in a rotation of the pulley at the fr'ee'end of the. arm -2 corre-. sponding to but in an opposite direction to the rotational movement of the arms I and 2.

The pulley at the free end of thearm 2 has secured thereto a scale support It which carries a pair of straight edges cr scales I! and I8.

With the structure thus far describ'ed, any "cvement of the scales I1 and IBoVer the board 8 will result in the scales being maintained in a fixed angular position with respect; to a baseline on the board 8.

To adjust the angular relation between the scales I! and I8 and such fixed base line, either the arm I or the arm 2 'may be shortened to loosen the frictional engagement of the band associated with that arm from the pulleys comprising a part of that arm. While both of the arms of" I and 2 may be adapted to be shortened to accomplish the release of its associated band,

'I preferto provide only one of thea'r ms with a quick-release mechanism which will' accoinplish observed that the rod I i of the arm 2 is assembled 'with'tlie headbracket I3 by means of a cam and follower mechanism which will permit a ready' a djustment of the length or the arm between a fully extended "position maintaining the band I5 in tight relation with the pulleys of the arm 2; and -a contracted position in which the 'band is so loosened'thatthe scale s'uppo'rtifi may be readily rotated without causing- 'a'corresponding rotationof the Pulley 9. j

The mechanism for assembling the 'rod' l l'and the head' bracket I3 preferably "comprises an adapter indicated generally by the reference character E9, the adapter comprisinga body portion telescopically engaged-within a socket 2i formed in the head'lt, the adapter in cluding a longitudinal cylindrical extension 2'2 adapted to ,be inserted into a bore 23 inthe rod It. In fact,

the'rod It may be constructed-"as a length of tube; the internalborejofwhich willfsnugly 'fit the cylindricalsurfa'ce qr extension 22. g

relative diameters "of the body portion 28 and the extension 22 arepreferablysuch that t e a d Qi t ed. or. tu e. .m r ss 'sli'ghtlywithin the socket 2I on the'head I3 to' th reby facilitate themanufacture and assembly ofthej adapter head and rodwithout exercising. extreme" care in maintaining accurata machine r e'e- Ihe adapter I9 is formed with a transverse slot 24 a lignablewith a slot '25 formed transversely through the end of the socket portion of the head I3 and through which extends a cam 26 to a position permitting it to be pivotally ful- V. crumed about a cross pin 21. The cam25, preferably comprises a relatively thin blade member formingtwo legs 28 and 290i alever. The leg 28 extends longitudinally ofthe arm Zwhen the lever is in its normal position, 'as shownin Figs. 2 and 3, the extremeend 30'of the.leg 28 being adapted to engage'the iend of acainfollower formed as a plunger 3| which is slidablymounted in the body 20 of theadapter 19.; I

a i a p e nd ii ie'P u ?i ileii e beyondthe end of the adapter I9 in to engagement with the head I3 as indicated at 32, so that when the cam is in the position shown in Figs. 2 and 3 the cam leg 28 will press the plunger 3| 5 against the head I3 in such fashion as to urge the head I3 and the rod I4' outwardly with respectto each other -and, elongatethejarm 2; to maintain i ,the fingers .of. the draftsmanand moved from the position shown in Figs. 2 and 3 to the position shown in Fig.4. When the'lever isin-the 20 position shown in Fig. 4', the maximum length of the cam leg. 28 1'is no,longer presenetd to -the plunger-'ZI-and: the plunger 15;:DEllIlitt8d to retract, relative tothe' adapterv 19., with the result that the adapter is moved inwardly inthesocket 2L resulting in th effective shortening-.-,-of the arm 2 and accomplishing-the releasepi the engagement between the band I 5 and the pulleys on the arm 2. 1 I

When theparts are in this positiong-the scales I I1 and I8 and their supportlfii rmaygbareadily rotated to a new angular positionw-ith; respect to the base line, whereupon movementpf. thelever Ztback to its- -normal:position so elongates the arm 22 as tore-engage'the bandtightly-withthe pulleys over-which-itistrained. and'the draiting machine is now ready .-for further operation-with the scales. correctly oriented to .-a new -angular V position'with respect to the base line; 1

,- To insure against the inadvertent loosening of V 40 the band I5 it is preferred to so shape thelever arn -ZB that when the lever 2 6is Hilts-"110111131 position a line drawn through the .maximum length; of the lever arm 28 and the center of the pivot pin 2'! engages'the-end of, the plunger 3| .45 at -a point above the longitudinal axis 10f the e plunger 3|, withithe result that the action isian over center action and the tension-:ofthe band I5 will act to hold the lever 26-mitsnormal position.:;

s5 o. facilitate the manipulation of the lever-26 there; may be provided lateral wings 34, extending {on opposite sides of the lever, extension 33,- the wings being preferably curved-to.conformwith -,the external curved surface of the rod or tube l4 7 soas to lie snugly about the rod or tube-. I4. .rFingerpieces 35 may beformed at the lower edges of the wingsfitto extend laterally thereof for .rnpre ready engagement by. the fingers of the draftsman. v p

so It will be observed therefore, thatlthere isprovided; a-ready mechanism for permitting-the adjustment of the angular position of the scaleson a drafting machine relativeto ai base line on the draftingboard by utilizing a, simple mechanism by which the effective length of one of the-articulated arms may bechanged sofasto readilyioosen the band from its pulleys and to restore the tight ened relation between the band and the pulleys when the scales have been moved to their new adjusted position; the essential; featuresofthe construction being the provision of a simplemechanism by which a relatively small movementiofa manipulating device, such as the leVer,- 6,will

cause a sufficient amount of contraction oithe 7 efiective neil .-Q heerm o sweeten them/end,

from its pulleys as to permit the ready adjustment of the protractor or scale support to a new oriented position.

While there has been shown and described the preferred embodiment of the present invention, the same is not to be limited to any of the details of construction shown or described herein except as defined in the appended claims.

What is claimed as new is:

1. In an articulated arm drafting machine of the band and pulley type having an arm construction including, a pair of pulleys, a pair of pulley supporting heads, a band trained over said pulleys, and a single strut rod interposed between said heads to hold said pulleys in such spaced relation as to maintain frictional engagement between said pulleys and band; the improvement of an adapter interposed between said strut rod and one of said heads for telescopically assembling said rod and head, a cam on said adapter, a plunger slidable in said adapter extending in the direction of the longitudinal axis of said arm and having its ends respectively engageable with said cam and said head, and means rotatably mounting said cam on said adapter for movement between one position urging said plunger against said head and another position permitting said plunger to retract from said head to thereby effect an extension and contraction of said arm to tighten or loosen said band relative to said pulleys.

2. In an articulated arm drafting machine of the band and pulley type having an arm construction including, a pair of pulleys, a pair of pulley supporting heads,'a band trained over said pulleys, and a single strut rod interposed between said heads to hold said pulleys in such spaced relation as to maintain frictional engagement between said pulleys and band, the improvement of an adapter interposed between said strut rod and one of said heads for telescopically assembling said 6 rod and head, a cam on said adapter, a plunger slidable in said adapter extending in the direction of the longitudinal axis of said arm and having its ends respectively engageable with said cam and said head, and pivot means extending transversely to the longitudinal axis of said arm for pivotally mounting said cam for movement between one position urging said plunger against said head and another position permitting said plunger to retract from said head to thereby effect an extension and contraction of said arm to tighten or loosen said band relative to said pulleys.

3. In an articulated arm drafting machine of the band and pulley type having an arm construction including, a pair of pulleys, a pair of pulley supporting heads, a band trained over said pulleys, and a single strut rod interposed between said heads to hold said pulleys in such spaced relation as to maintain frictional engagement between said pulleys and band; the improvement of an adapter interposed between said strut rod and one of said heads for telescopically assembling said rod and head, a cam on said adapter, a plunger slidable in said adapter extending in the direction of the longitudinal axis of said arm and having its ends respectively engageable with said cam and said head, and a handle on said cam for actuating the same, said handle being disposed relative to said cam to extend in a position parallel to said strut rod when said cam is in strut lengthening position.

JOHN A. HISLOP.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,051,115 Wallace Aug. 18, 1936 2,243,732 Eubanks May 27, 1941 

